Array elements as counters

[abhishekphukan]

import java.util.Random;
public class apples {
	
	public static void main(String args[]){
		Random rand= new Random();
		int freq[]=new int[7];
		
		for(int roll=1;roll<1000;roll++){
			int index = 1+rand.nextInt(6);
			int f = freq[index];
			++f;
			freq[index] = f;
		}
		
		System.out.println("Face \tFrequency");
		
		for(int face=1;face<freq.length;face++){
			System.out.println(face+"       "+freq[face]);
		}
	}
}

Please can someone explain the first (for loop)of the program...with an appropriate example will be really helpful.
Thank You.